In recent years, an automatic toll collecting system has been developed which utilizes a toll pre-paid type card or a toll post-payment type card to receive charges for using charged facilities, for example, to receive a toll charged on a toll road. In the automatic toll collecting system, on-road apparatuses for road-to-vehicle communications (hereinafter referred to as “on-road apparatuses”) with antennas, each of which serves as an interrogator for making inquiries with respect to a vehicle for information in order to collect tolls automatically at entrance and exit gates of the toll road, are provided on the road side, and each of vehicle-mounted apparatuses for road-to-vehicle communications communications (hereinafter referred to as “vehicle-mounted apparatuses”) with antennas, each of which serves as a responder for responding to the information, with respect to which an inquiry was made is mounted on the vehicle, whereby the information is transferred by radio communications between the vehicle-mounted apparatus and the on-road apparatus.
In order to transfer the information between the vehicle-mounted apparatus and the on-road apparatus, toll information or vehicle information about a vehicle, and information about a user must be stored. For this reason, an IC card in which a large quantity of data can be stored may be used with information being written therein.
However, as described above, when the information is transferred between the vehicle-mounted apparatus and the on-road apparatus or when the information is transferred to and received from the IC card, the information is used with a form thereof left unchanged. As a result, there exists a problem that a person not intended by a user can easily disclose contents of the information.
Accordingly, there has been proposed an electronic identification system in which secrecy is kept by identifying that a transmitted secret code such as an inherent code coincides with at least one of a plurality of predetermined secret codes, thereby resulting in improvement of security (see Japanese Patent Application Laid-Open (JP-A) No. 6-511097).
However, in a conventional electronic identification system, only one kind of secret code is assigned to a user, and therefore, secret codes must be set correspondingly to the number of users so as to identify a great number of users. For this reason, in a road-to-vehicle communication device in which information is transferred to and received from each of a great number of users, the load on the device increases. Further, only one kind of secret code is assigned to a user, and therefore, when the secret code leaks out, the security of a system used by the user, namely, of the road-to-vehicle communication device, deteriorates.
Further, in order to collect a toll automatically by transferring information between the vehicle-mounted apparatus and the on-road apparatus, vehicle information about a vehicle and user information about a user, such as a balance of charges for accounting must be stored. Accordingly, the IC card in which a large quantity of data can be stored may be used with information being written therein.
However, in a case of transferring the above-described information, when the information is used in a general description form, there exists a problem that a person that is not intended by a user or an information provider can illegally alter or falsify the contents of the information and can also unlawfully utilize such information.
Accordingly, there has been proposed an automatic toll collecting system in which information communicated between an on-road apparatus and a vehicle-mounted apparatus is encoded so as to improve the security (see Japanese Patent Application Laid-Open (JP-A) No. 6-60237). In this system, encoded information stored in an IC card or encoded information from the on-road apparatus is made into a common sentence structure (made into a general descriptive form) in the vehicle-mounted apparatus, and processing for user information such as a balance of charges is effected.
However, in the conventional automatic toll collecting system, the user information made into a common sentence structure in the vehicle-mounted apparatus is temporarily stored. Accordingly, a person that is not intended by the user or the information provider can easily falsify the contents of the user information about a user such as the balance of charges, and the like, thereby resulting in deterioration of security.